1. Field of the Invention
This invention relates to a novel epoxidized polyether.
2. Description of the Prior Art
Most of epoxy resins now industrially produced comprise an epoxy compound of bisphenol A type as the main constituent, and are widely used in fields of electrically insulating materials, coating materials, laminates, structure materials, materials for civil engineering and construction, and the like by taking advantage of characteristics of the epoxy resins such as toughness, heat resistance, chemical resistance, adhesion, etc. This is because epoxy resins of bisphenol A type have, in the molecule, not only highly reactive epoxy groups but also bisphenol A residues capable of imparting heat resistance and hydroxyl groups capable of imparting adhesion. There are found substantially no other resins having such various characteristics. The epoxy compound as the main constitutent is hardly used alone and, in usual, it can exhibit excellent characteristics by incorporation of additives, for example, curing agents such as polymethylenediamine, polyetherdiamine, isophoronediamine, methaphenylenediamine, 2,4-toluenediamine, phthalic anhydride, maleic anhydride and the like; reactive diluents such as styrene oxide, glycidyl methacrylate, allyl glycidyl ether, diglycidyl ether and the like; fillers such as silica, mica, quartz powder and the like; and cure accelerators such as phenol, bisphenol A, salicylic acid, tin octylate and the like.
Various characteristics can be imparted to epoxy resins by properly adjusting the kinds and amounts of these additives, and this is one of the reasons why epoxy resins are used for various purposes.
Epoxy resins have excellent characteristics as described above, but with the development of required performance characteristics in various uses, it has become apparent that they still have various points required to be improved. One of the points is that conventional epoxy resins are poor in flexibility. That is to say, epoxy resins of bisphenol A type are generally poor in softness, and particularly when they are used in coating materials for elastic body, cracks are very liable to be formed. This has been an industrially serious defect.
Under these circumstances, extensive research has come to be conducted on imparting a high flexibility to epoxy resins. As one aspect of the research, there is known a method by which an elastomer is merely blended with epoxy resins. However, this method requires sufficiently reproducible dispersion of an elastomer having a suitable particle size, and hence, is technically very difficult and industrially very disadvantageous. Accordingly, research has gradually become active on reactive flexibility-imparting agents having in the molecule an elastic skeleton for imparting a high flexibility to epoxy resins, and various flexibility-imparting agents have been developed.
However, under the existing circumstances, there has not yet been obtained any flexibility-imparting agent which is satisfactory in all of the miscibility with an epoxy compound as the main constituent or a curing agent, various characteristics of the epoxy resin such as mechanical characteristics, impact resistance and the like, and the production cost thereof.
On the other hand, polyoxytetramethylene glycols known as materials for polyurethanes and polyesters are, in general, produced by subjecting tetrahydrofuran to ring-opening polymerization. Polyoxytetramethylene glycols are reactive polymers in which a hydroxyl group is attached to either end of the molecule, and particularly when they are used as materials for polyurethanes and reacted with a diisocyanate, the resulting polyurethanes are superior to those obtained by using other polymer glycols as materials in mechanical characteristics and hydrolysis resistance. Therefore, polyoxytetramethylene glycols have come to be widely used as industrially important materials. Polyoxytetramethylene glycols have a structure in which its skeleton comprises regularly repeated oxytetramethylene units, and this is presumed to make the mechanical characteristics and strength excellent.
In view of the circumstances described above, the present inventors have conducted extensive research to find that epoxidized polyethers containing oxytetramethylene units give an epoxy resin having a high flexibility and moreover various excellent characteristics.